bugs on variant id

controllers/productController.go

@@ -416,6 +416,22 @@ func (ctl *ProductController) GetProductByVariant(c *fiber.Ctx) error {
 	// nothing to work with.
 	productID, _ := strconv.Atoi(c.Query("productid"))
 
+	// One of the two has to name something, and `variantid=0` names nothing.
+	//
+	// 0 is not a variant group — it is the value every UNGROUPED product
+	// carries, so a query for it used to match the tenant's whole ungrouped
+	// catalogue and return six unrelated products as each other's variants. The
+	// ordering screen then had a list it could not choose from, and no order
+	// could be placed. Refusing here turns that into one sentence naming the
+	// parameter to send instead.
+	if variantid <= 0 && productID <= 0 {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"code":    http.StatusBadRequest,
+			"status":  false,
+			"message": "send productid (preferred) or a variantid above 0 — variantid 0 is not a variant group, it is what every ungrouped product carries",
+		})
+	}
+
 	result, err := ctl.productService.GetProductByVariant(tenantID, variantid, locationID, productID)
 
 	if err != nil {
@@ -535,6 +551,33 @@ func (ctl *ProductController) CreateProductLocation(c *fiber.Ctx) error {
 	})
 }
 
+// UpdateProductVariant puts a product into a variant group, or takes it out.
+//
+// variantid 0 means ungrouped and is allowed — it is a real thing to want. The
+// read path is what refuses to treat 0 as a group to search for.
+func (ctl *ProductController) UpdateProductVariant(c *fiber.Ctx) error {
+	var body struct {
+		Productid int `json:"productid"`
+		Variantid int `json:"variantid"`
+	}
+	if err := c.BodyParser(&body); err != nil {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"code": http.StatusBadRequest, "status": false, "message": "Invalid request body",
+		})
+	}
+	if body.Productid <= 0 {
+		return c.Status(fiber.StatusBadRequest).JSON(fiber.Map{
+			"code": http.StatusBadRequest, "status": false, "message": "productid is required",
+		})
+	}
+	if err := ctl.productService.UpdateProductVariant(body.Productid, body.Variantid); err != nil {
+		return c.Status(fiber.StatusConflict).JSON(fiber.Map{
+			"code": http.StatusConflict, "status": false, "message": err.Error(),
+		})
+	}
+	return c.JSON(fiber.Map{"code": http.StatusOK, "status": true, "message": "Success"})
+}
+
 func (ctl *ProductController) CreateProductVariant(c *fiber.Ctx) error {
 	var input models.Productvariant